1. Field of Invention
The present invention relates to a torque-exerting device and, more particularly, to a clutch for a torque-exerting device.
2. Related Prior Art
There are various torque-exerting devices such as screwdrivers and wrenches. These torque-exerting devices can be classified into hand tools and automatic tools. The automatic tools can be classified into pneumatic and electric tools. Some of the torque-exerting devices include clutches to transmit predetermined values of torque.
The clutches can be classified into a ratchet-type and a ball-type. A ratchet-type of clutch includes a movable element and a rotatable element. The movable element includes ratchets for releasable engagement with ratchets of the rotatable element. In use, the movable element is placed in a handle for example so that the former is movable up and down in the latter. The rotatable element is placed in the handle so that the former is rotatable in the latter. The rotatable element is engaged with a bit. A predetermined value of torque can be transferred to the bit from the handle via the clutch. Under the predetermined value of torque, the ratchets of the movable element are engaged with the ratchets of the rotatable element for transmitting the torque. At the predetermined value of torque, the ratchets of the movable element are disengaged from the ratchets of the rotatable element. When the ratchets of the movable element are disengaged from the ratchets of the rotatable element, the movable element is moved up and down in the handle. The movable element tends to wear away the handle.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.